1. Field Art
The disclosure generally relates to the field of a virtual model generation, and in particular to a computer implemented process of generating a three dimensional virtual model.
2. Background Information
Three dimensional (3-D) models provide ease of understanding of objects with complex shapes. Through a computer generated virtual 3-D model of a 3-D object, shapes and arrangements of various components of the object from different points of views can be visually presented. Additionally, the 3-D model can be modified to simulate a case in which the object is modified or repositioned. Moreover, the 3-D model can be rendered into a tangible replica through a 3-D printer.
In one example, a 3-D model can be generated based on 2-D cross-sectional images (e.g., computerized tomography (CT) scan or magnetic resonance imaging (MRI) scan images). FIG. 1 illustrates an example CT scan image 100 of a head of a human subject including objects 110, 120, 130, 140, 160, 180 (e.g., temporomandibular joints 110, 180, vertebral foramen 120, vertebra 130, and teeth 140, 160). Example objects include bones, teeth, or any body parts for determining a medical status of the subject.
FIGS. 2A and 2B illustrate an example conventional process of generating a 3-D model from two CT scan images. In a conventional approach, edges of objects 110A, 130A, 140A, 160A, and 180A of a first CT scan image are extracted, and edges of corresponding objects 110B, 130B, 140B, 160B, and 180B of a second CT scan image are extracted. By connecting corresponding edges, surfaces 215, 235, 245, 265, and 285 of 3-D models 210, 230, 240, 260, and 280 can be generated. Accordingly, the 3-D models 210, 230, 240, 260, and 280 corresponding to objects 110, 130, 140, 160, and 180, respectively, can be obtained.
However, a 3-D model generated through the conventional approach cannot represent objects placed within another object. For example, by extracting the edges 130A, 130B and generating the surface 235 by connecting the edges 130A, 130B, the object 120 within the object 130 is ignored. Accordingly, a 3-D model obtained through the conventional approach cannot accurately represent objects that are enclosed or surrounded by other objects.
Moreover, a 3-D model generated through the conventional approach may have an unclosed (or open) shape. In the conventional approach, if two edges are determined to be not part of a same object, a surface between two edges is omitted. The absence of a closed surface becomes a hole, thereby resulting in the open shape. For example, as shown in FIG. 3, holes 310A . . . 310F are generated, because edges around the holes 310 are determined to be part of different objects. Such open shapes due to these holes in the 3-D model cause inner parts of the objects and external parts of the objects to be indistinguishable. As a result, the 3-D model with an open shape cannot be 3-D printed or causes inaccurate 3-D printing of the 3-D model.